The present invention relates to a device for determining the relative position of a reference axis of an object with respect to a spatially fixed and substantially parallel focused reference beam of electromagnetic radiation, particularly a laser beam, directed thereto.
In the known devices of this kind, the partial beam is branched off at a right angle to the incident primary reference beam. In the known device, which is housed in the measuring head of an industrial robot for its laser-guided control (DE-A1 37 10 068), the position detector, onto which impinges the reference beam traversing the splitting mirror rectilinearly, serves the ascertaining of redispositions of the measuring head perpendicularly to the reference beam, whilst the other position detector, on which impinges the partial beam branched off at right angles, fulfills the purpose of delivering signals which are proportional to the rotation of the measuring head around the reference beam. An enlarging lens inserted into the beam path of the reference beam is so dimensioned that it effects an enlargement of the X direction and the Y direction on the first-mentioned position detector and the spacings of both the position detectors from the splitting mirror are arranged to be differently large, wherein the position detector hit by the reference beam is arranged near to the splitting mirror and the other position detector displays a substantially larger spacing herefrom perpendicularly to the reference beam. The consequence is that the known device displays a large space requirement in direction perpendicular to the laser beam.
The invention is based on the task of creating a device for determining the relative position of a reference axis of an object with respect to a spatially fixed and substantially parallel focused reference beam of electromagnetic radiation, particularly a laser beam, directed thereto, which has a substantially lower space requirement than the known devices and nevertheless displays a large effective length difference for the spacings between the measurement points on the measurement object so that it can be used with great resolving capability and great accuracy for the ascertaining of parallel displacements as well as also of angular displacements of the reference axis of the measurement object relative to the reference beam.
In the device according to the invention, an appreciably increased spacing is achieved geometrically between the measurement points at the object, namely the direct measurement point in the beam path of the reference beam and the virtual measurement point in the beam path of the partial beam, already with optimally small space requirement for the device due to the folding of the branched-off partial beam effected by the special kind of the twofold reflection of the same and this length difference is still enlarged optically by the dimensioning of the optical enlarging system especially adapted for this purpose.
A particularly compact and also interference-proof build-up of the device according to the invention is achieved by the convergent optical system being arranged in front of the splitting mirror in the beam path of the reference beam and by the convergent optical system being cemented together with the splitting mirror and the deflecting mirror as well as with the position detectors into a compact optical glass system, for which purpose the convergent optical system for the optical enlargement of the measurement point spacing is installed in the beam path at the entry side of the compact optical glass system, thus already in front of the splitting mirror.
Rotations of the device about the axis of the reference beam as well as the spacing of the device from the radiation transmitter can be detected in the device according to the invention by the fact that the radiation transmitter emits two reference beams, which between them include an acute angle, towards the object that both impinge on the position detectors. The separation of both the penetration points of both the reference beams impinging on each detector can on appropriate choice of the position detectors be left to them. It is however particularly advantageous so to equip the radiation transmitter that it emits both the reference beams in alternation so that simpler biaxial position detectors can be used.
The invention is explained still more closely in the following by an example of embodiment with reference to the drawing.